This invention relates generally to material handling apparatus, and more particularly to a system for handling powdered or fine granular, fluent materials, the system enabling ready unloading of the material from a container without the formation of clumps of material or air pockets.
The unloading system of the present invention is particularly adapted for use with containers disclosed in U.S. Pat. Nos. 3,777,775, 4,007,694 and 4,182,386, which are commercially available from Semi-Bulk Systems, Inc., St. Louis, Mo., under the registered trademark "Air Pallet". The disclosure of the aforementioned patents is incorporated herein by reference. These containers have a rigid molded plastic pallet base and a flexible plastic film bag, are used to receive, transport and unload "semi-bulk" (e.g., 2,000-4,000 pounds or more) of powdered or finely divided granular material. Systems for loading and unloading such containers are disclosed in the U.S. Pat. Nos. 4,182,386 and 4,054,161 (the latter of which is also incorporated herein by reference).
The present system for unloading a container of the aforementioned type involves the injection of compressed air into the container for fluidizing the granular material to facilitate its flow out of the container through an outlet. In some instances, the material in the container may be difficult to fluidize (as in the case of certain powders densely compacted in the container), in which case the material tends to clump and to "bridge" the walls of the container to form air pockets. This hinders and may even prevent complete emptying of the container. Thus, there is presently a need for a system for efficiently and completely unloading powdered or granular materials of this type.